1. Field of the Invention
The present invention generally relates to a capacitor and, more particularly, to a compact capacitor having multiple anodes.
2. Prior Art
Certain types of capacitors, such as a wet tantalum capacitor, may be designed and built to contain multiple anodes. Prior to being assembled into an external case, each anode is sealed inside a polypropylene and/or another separator material. For some applications in which the capacitor may be inserted into the vasculature of a patient, the overall capacitor configuration may be cylindrical with an aspect ratio (i.e. length:diameter ratio) much greater than one. The aspect ratio may be 10 or more. To obtain high energy density in the capacitor, the net combined shape of the anodes contained therein may also be cylindrical with comparable aspect ratios.
For example, U.S. Pat. No. 7,072,171 to Muffoletto et al., which is assigned to the assignee of the present invention and incorporated herein by reference, describes a capacitor comprised of a casing having a cylindrical casing sidewall extending to closed opposed first and second end walls; and a first anode and a second anode, each comprising a radiused anode sidewall portion meeting a planar sidewall portion extending to first and second anode end walls, wherein the anodes are in a side-by-side relationship having the respective planar sidewall portions facing each other. The capacitor further includes a cathode comprising a conductive substrate having first and second major faces supporting a cathode active material which opposes the sidewalls of the first and second anodes. The first and second anodes include respective anode leads extending from their first end walls. The anode leads are joined to a terminal pin provided between the anodes and the first end wall of the casing.
Additionally, U.S. patent application Ser. No. 61/050,716, filed May 6, 2008, which is assigned to the assignee of the present invention and incorporated herein by reference, discloses a capacitor with a casing having a cylindrical casing sidewall extending to closed first and second end walls, and an anode assembly including first, second and third anodes. Each anode comprises a surrounding sidewall extending to first and second anode end walls and a conductive lead extending therefrom. The anodes are in a side-by-side relationship within the casing with their respective sidewalls parallel to each other.
There is a benefit to providing a capacitor with multiple anodes, i.e. more than one anode, because subdividing the anode material mass and providing corresponding opposed cathode material increases the overall active surface area of the capacitor electrodes. Thus, a greater overall capacitance can be attained within the same casing volume. However, each anode lead must be electrically connected to a common anode terminal pin in a compact space. Accordingly, “multiple anode lead management” for capacitor configurations that include two or more anodes becomes critical in the overall capacitor design.
There is, therefore, a need to minimize the amount of non-active intradevice volume being utilized for connection between the anode leads and the terminal pin, and the adjoining glass-to-metal-seal (GTMS) assembly that seals and electrically insulates the terminal pin to the capacitor casing. There is also a need for a robust method for interconnection of multiple anode leads to the positive termination, i.e. the terminal lead.